RESUMO
A facile and efficient cyclization of sodium aminodiboranate to construct a boron-nitrogen-hydrogen ring is presented. This new strategy can be developed into a general method to prepare aminodiborane and its derivatives. Theoretical calculations show that a one-step cyclization mechanism is favored, where the dihydrogen bond plays an important role.
RESUMO
OBJECTIVE: The purpose of this study was to analyze factors for their ability to predict multiple gestation in women who undergo controlled ovarian hyperstimulation with gonadotropins (follicle-stimulating hormone/human menopausal gonadotropin) and intrauterine insemination. STUDY DESIGN: This was a retrospective analysis of the clinical and laboratory variables that are associated with multiple gestation. Data for 6 variables in 678 cycles of gonadotropin/intrauterine insemination between 1990 and 1999 were analyzed with survival analysis, Cox regression analysis, and multiple logistic regression. RESULTS: There were 99 clinical pregnancies among 678 cycles (14.6% per cycle) in 306 women. Of the 14 women with multiple gestations (14.1% of pregnancies), 11 women had twins, 2 women had triplets, and 1 woman had quadruplets. Age, days of gonadotropin treatment, total dose of gonadotropin, and number of follicles that were >or=15 mm at the time of human chorionic gonadotropin administration were statistically significant predictors of multiple gestation in >or=1 of the statistical models. CONCLUSION: The risk of multiple gestation with controlled ovarian hyperstimulation/intrauterine insemination in this study was relatively low. In addition to age, several controllable variables that are associated with multiple gestation were identified.
